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Abstract:

Hypothesis / aims of study There are not much data on in vivo biomechanical measurements of the vaginal wall. Epstein et al (1) examined the relationship of in vivo biomechanical properties of the vaginal wall in patients with and without prolapse. In that study, as having prolapse were considered patients in whom the leading edge descended beyond the hymenal ring. Measurements were done on a single point on the lateral vaginal wall 2 cm above the hymenal ring. They used the commercially available DermaLab skin probe (Cortex Technology, Hadsund, Denmark; dimensions: 2.0*1.5 cm). During measurement, the vaginal wall is subjected to an increasing aspiration pressure. It registers the time it takes the vaginal epithelium to pass through a 10 mm aperture as evidenced by an infrared light beam. This device however is not purposely designed for intravaginal use. It has a large aperture, so that compliant tissue could fill the cup prior to measurement. Also measurements are done at a single point, which on itself is not a reference point of the clinical POP-Q score (2) . Herein we aimed to perform site specific in vivo biomechanical properties with a purpose-designed suction device, derived from the Cutometer MPA 580 (Courage and Khazaka Electronic GmbH, Cologne, Germany). This device is designed for intravaginal use, has a length of 20 cm and the largest diameter of the device is 3 cm and a 6. In essence, it records vaginal wall displacement (strain) under a fixed aspiration pressure (stress) through an integrated optical system. Study design, materials and methods A total of 48 patients, in which we could obtain at least one recording, were included in this study. These were women referred for pelvic floor ultrasound examination for a variety of reasons. First, the degree of prolapse was staged according to the POPQ-classification, and categorized as stage I or less (not prolapsed) or stage II or more (prolapsed). Then vaginal biomechanical properties were measured using the device. One typical vaginal elasticity measurement consisted of a single cycle with an aspiration pressure of 300 mbar, an aspiration pressure comparable to dermal measurements. Both suction and relaxation time consist of 5 sec after an initial 10 sec pretime without aspiration. The measurements were taken at four places: two on the anterior vaginal wall, at point Aa and 5 cm above the hymenal ring (=Aa-2 cm), and two on the posterior wall, at point Ap and 5 cm above the hymenal ring (=Ap-2 cm). The Cutometer MPA580 software displays a series of plots and parameters (=recording), among which R0: firmness of the vaginal wall; R2: overall elasticity and R7: ratio of elastic recovery to the total deformation, which are representative for the entire measurement. After measurement, the recording was judged to be interpretable or not, based on its quality. If not, up to three attempts were made to obtain a better recording. In its absence, the entire measurement for this location was classified as failed. Further their medical records were searched for history of prolapse surgery. Descriptive statistics and factor analysis were done using, JMP®7 software (SAS Institute Inc., Cary, NC, 2007). Factor analysis allows to determine which experimental conditions affect the measurements in a significant way and which experimental conditions could be considered as irrelevant. Results The mean age of patients was 64,27 years (range:28-82 yrs). The summary statistics of these are displayed in Table 1. None of the correlations between clinical prolapse scores and the biomechanical measurement values (R0, R2, R7) were significant (p values not shown). Measurements within the same patient, at different sites, were significantly correlated (p>0.05). Further we observed that measurements in patients previously operated for prolapse, as compared to those never operated for prolapse, were significantly different as demonstrated in table 2. Of note is that measurements in patients with a previous operation, measurements of all sites, even if unoperated, were comparable. However that number of sites was so low that no further statistics were run on it.